Public-safety and critical infrastructure industries (CII) entities received backing from the National Football League (NFL) and vehicle-to-everything (V2X) proponents in opposing unlicensed operations in the 6 GHz band. However, heavyweights such as Boeing, Apple and other high-tech firms are all advocating for the FCC to open the band to unlicensed users.

The NFL relies on 6 GHz spectrum for ultra-wideband (UWB) technology that enables real-time player tracking at NFL stadiums and other facilities. The NFL urged the commission to protect use of UWB technology, along with 6 GHz applications for broadcast and public safety. “The NFL urges the commission to ensure that any newly authorized devices do not cause harmful interference to incumbent users — both licensed and unlicensed — in the 6 GHz band,” the comments aid.

BMW Group supports the use of the 5.9 GHz band for cellular-V2X (C-V2X) services and said it supports a waiver to allow C-V2X operations in the upper 20 megahertz of the 5.9 GHz band. “The proposed out-of-band-emission limit for unlicensed operations in the 6 GHz band would likely cause harmful interference to safety-related C-V2X services,” BMW said in its comments. “Given the potential of C-V2X services to dramatically improve safety on America’s roads, this seems like an unnecessary potential risk to safety-relevant communication.”

The American Association of State Highway and Transportation Officials (AASHTO) also supports V2X operations and noted its concerns regarding interference from 6 GHz unlicensed operations.

Public-safety groups including the National Public Safety Telecommunications Council (NPSTC), the California Public-Safety Radio Association (CPRA) and the city of Los Angeles, among others all filed comments opposing unlicensed 6 GHz use, citing numerous interference concerns to public-safety 9-1-1 facilities and base stations. The groups said further engineering studies are necessary to validate potential interference from the FCC’s proposed changes.

NPSTC supported Motorola Solutions’ suggestion of using -12 dB interference to noise (I/N) ratio as the threshold for interference.

In its reply comments, the Enterprise Wireless Alliance (EWA) underscored concerns about the potential for interference within the 6 GHz band. “EWA does not oppose sharing but, given the importance of reliable communications for these services, will assent to sharing only if it can be demonstrated that appropriate measures are in place to prevent interference at the outset of sharing, not when it occurs later,” the group said.

EWA said it is particularly concerned that insufficient consideration has been given to what happens in the event of interference, noting the FCC’s NPRM on the 6 GHz changes devotes only a paragraph — five sentences — to this critical discussion.

“Who is responsible for shutting down secondary consumer devices and for the resulting liability?” EWA asked. “There are out-of-pocket costs incurred in identifying and resolving interference problems for which someone must be accountable. Since these unlicensed devices have only secondary rights in the band, does the automated frequency coordinator (AFC) with which they are registered have operational and financial responsibility for the interference they cause? Will the FCC adopt rules regarding how quickly AFCs must respond to interference complaints? Will an AFC be held legally responsible for any negative repercussions that result should they shut down an unlicensed device?”

The Utilities Technology Council (UTC), the American Petroleum Institute (API), the American Public Power Association (APPA), the American Water Works Association (AWWA), the Edison Electric Institute (EEI), and the National Rural Electric Cooperative Association (NRECA) highlighted the large number of microwave systems at 6 GHz that are built to maintain 99.999 percent reliability for utilities and other CII users. The groups said interference protections should be high and provided recommended improvements to the AFC to ensure interference protections for indoor and outdoor devices.

Pacific Gas & Electric Co. (PG&E) said additional and real-world testing is required before any rules changes are finalized. “The mere possibility of introducing harmful interference and impacting vital communications for private fixed users should be cause enough for the FCC to consider more in-depth testing before proceeding with any of the proposed changes,” the utility said.

AT&T said the AFC system must provide near-perfect interference protection to incumbent 6 GHz systems.

However for every filing opposing unlicensed use at 6 GHz, another filing supported unlicensed use, including comments from Boeing; Apple; and a combined group of technology companies including Apple, Facebook, Google, Microsoft, Qualcomm and others, which said the record supports the FCC’s proposal to permit unlicensed use in the 6 GHz spectrum. CTIA and T-Mobile want more licensed spectrum in the band for carriers and said the FCC should evaluate relocating existing 6 GHz licensees in the band to other spectrum to make that happen.